I want to improve the glowing effect in the MWE below. As shown in the output there is like a sharp transition between the white circle in the center and the surrounding halo, which does not give the desired effect of having a smooth transition to simulate a natural light. I don't know how TikZ enthusiasts would approach this matter in order to improve the glowing effect? in other words, how far TikZ can go with the glowing effect?

Note
Please keep the diameter of all circles fixed, but you can adjust fading width, the most important point is not to show the empty space at the confluence of the colored circles, I want it to be completely hidden behind the white glowing light, I hope.